CFD Online Logo CFD Online URL
Home > Forums > Main CFD Forum

Time accuracy of NITA - FRACTIONAL STEP in Fluent

Register Blogs Members List Search Today's Posts Mark Forums Read

LinkBack Thread Tools Display Modes
Old   March 19, 2008, 08:20
Default Time accuracy of NITA - FRACTIONAL STEP in Fluent
Paolo Lampitella
Posts: n/a

i'm trying to perform some accuracy tests of the NITA - FRACTIONAL STEP time integration scheme employed in Fluent using the Taylor Test Case, which is a double periodic array of vortex whose kinetic energy is decaying in time.

I performed several simulations with several grids, domains, boundary conditions, pressure interpolation schemes and space discretizations but i have misleading results.

Using exactly the same conditions cited in the paper (relative to this scheme used in Fluent):

Sung-Eun Kim Boris Makarov

An Implicit Fractional-Step Method for Efficient Transient Simulation of Incompressible Flows

AIAA 2005-5253

i obtain the same results cited there, a 2nd order accurate in time scheme.

But, just going outside the conditions cited there, just using one more point in the error curve, i always obtain only a first order time accurate scheme or even worst convergence.

So i'd like to know if someone has experience in this or even know if there are some other papers where the scheme has been more rigorously tested and with which compare my results. Obviously, i mean the scheme implemented in Fluent and not just the Fractional Step.

This scheme, in particular, seems to be a fully implicit, approximate factorization, fractional step method with incremental pressure approach. It also seems that the boundary condition for the pressure equation is simply dp/dn = 0 and i don't know if in this particular case it is correct (i think it isn't)

Thanks a lot, any help is appreciated

  Reply With Quote


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
Orifice Plate with a fully developed flow - Problems with convergence jonmec OpenFOAM Running, Solving & CFD 3 July 28, 2011 05:24
Computational time sunnysun OpenFOAM Running, Solving & CFD 5 March 16, 2009 04:32
Time Accuracy of the NITA - FRACTIONAL STEP method Paolo Lampitella FLUENT 1 March 19, 2008 06:45
determination of time step in transient simulation Guillaume Jolly Main CFD Forum 3 April 9, 2007 20:13
unsteady calcs in FLUENT Sanjay Padhiar Main CFD Forum 1 March 31, 1999 12:32

All times are GMT -4. The time now is 05:25.